Optical imaging system

ABSTRACT

An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from an object side to an imaging plane. An object-side surface of the fourth lens is convex, an object-side surface of the fifth lens is concave, and an angle of view of the optical imaging system is 100 degrees or more.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/139,259filed on Sep. 24, 2018, now U.S. Pat. No. 10,823,941 issued on Nov. 3,2020, which is a continuation of application Ser. No. 15/585,265 filedon May 3, 2017, now U.S. Pat. No. 10,156,703 issued on Dec. 18, 2018,and claims the benefit under 35 USC 119(a) of Korean Patent ApplicationNo. 10-201 6-01 80325 filed on Dec. 27, 2016, in the Korean IntellectualProperty Office, the entire disclosures of which are incorporated hereinby reference for all purposes.

BACKGROUND 1. Field

The following description relates to an optical imaging system.

2. Description of Related Art

In mobile terminals, camera modules have come to be provided as astandard component, enabling video calls and image capture. In addition,as the functionality of camera modules in portable terminals hasgradually increased, demand for high-resolution, high-performance cameramodules in portable terminals has also increased. However, becauseportable terminals are becoming miniaturized and lightweight,limitations in implementing high-resolution and high-performance cameramodules have been encountered.

In order to implement miniature high-performance modules, the lenses ofcamera modules have been formed of a plastic material lighter thanglass, and optical imaging systems include five or more lenses toimplement high resolution. Other considerations must also be factoredinto the design in the case of camera modules installed on the frontsurfaces of portable terminals. Such camera modules use a relativelywide angle of view to capture wide-range images.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, an optical imaging system includes a first lens,a second lens, a third lens, a fourth lens, a fifth lens, and a sixthlens sequentially arranged from an object side to an imaging plane. Anobject-side surface of the fourth lens is convex along an optical axis,an object-side surface of the fifth lens is concave along the opticalaxis, and an angle of view of the optical imaging system is 100 degreesor more.

The optical imaging system may satisfy the expression 0.5<f/f3<5.0,where f3 represents a focal length of the third lens is f3 and frepresents a total focal length of the optical imaging system. Theoptical imaging system can satisfy the expression 20<v1−v6<60, where v1represents an Abbe number of the first lens is v1 and v6 represents anAbbe number of the sixth lens. The optical imaging system may satisfythe expression 0<TTL/FOV<0.1, where TTL represents a distance from anobject-side surface of the first lens to an imaging plane of an imagesensor and FOV represents the angle of view of the optical imagingsystem. The optical imaging system can satisfy the expression1.60<n4<2.10, where n4 represents a refractive index of the fourth lens.

The optical imaging system may further include a stop disposed betweenthe second lens and the third lens. One or both of an object-sidesurface or an image-side surface of the sixth lens of the opticalimaging system can be aspherical.

The optical imaging system may be configured where the first lens has anegative refractive power and a convex object-side surface along theoptical axis, the third lens has a positive refractive power, the fourthlens has a negative refractive power, the fifth lens has a conveximage-side surface along the optical axis, and the sixth lens has anegative refractive power and a concave image-side surface along theoptical axis. The optical imaging system can be configured where thefirst lens has a negative refractive power, the second lens has apositive refractive power, the third lens has a positive refractivepower, the fourth lens has a negative refractive power, the fifth lenshas a positive refractive power, and the sixth lens has a negativerefractive power.

The first lens of the optical imaging system may have a negativerefractive power, a convex object-side surface along the optical axis,and a concave image-side surface along the optical axis. The second lensof the optical imaging system can have a positive refractive power, aconvex object-side surface along the optical axis, and a concaveimage-side surface along the optical axis. The third lens of the opticalimaging system may have a positive refractive power and both surfaces ofthe third lens may be convex along the optical axis.

The fourth lens of the optical imaging system may have a negativerefractive power and a concave image-side surface along the opticalaxis. The fifth lens of the optical imaging system can have a positiverefractive power and a convex image-side surface along the optical axis.The sixth lens of the optical imaging system may have a negativerefractive power, a convex object-side surface along the optical axis,and a concave image-side surface along the optical axis.

In another general aspect, an optical imaging system includes a firstlens having a negative refractive power and having a convex object-sidesurface, a second lens, a third lens having a positive refractive power,a fourth lens having a negative refractive power, a fifth lens having aconvex image-side surface, and a sixth lens having a negative refractivepower and having a concave image-side surface. The first to sixth lensesare sequentially arranged from an object side to an imaging plane. Theexpression 0.5<f/f3<5.0 is satisfied, where f represents a total focallength of the optical imaging system and f3 represents a focal length ofthe third lens.

In another general aspect, an optical imaging system includes a firstlens having a concave image-side surface and a second lens, a thirdlens, a fourth lens, a fifth lens, and a sixth lens. The first to sixthlenses are sequentially arranged from an object side to an imagingplane. An F-number of the optical imaging system is 2.45 or less.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a lens configuration diagram illustrating an optical imagingsystem according to a first example.

FIG. 2 is a set of graphs illustrating curves representing aberrationcharacteristics of the optical imaging system illustrated in FIG. 1 .

FIG. 3 is a table listing lens characteristics of the optical imagingsystem illustrated in FIG. 1 .

FIG. 4 is a table listing aspherical coefficients of lenses of theoptical imaging system illustrated in FIG. 1 .

FIG. 5 is a lens configuration diagram of an optical imaging systemaccording to a second example.

FIG. 6 is a set of graphs illustrating curves representing aberrationcharacteristics of the optical imaging system illustrated in FIG. 5 .

FIG. 7 is a table listing lens characteristics of the optical imagingsystem illustrated in FIG. 5 ; and

FIG. 8 is a table listing aspherical coefficients of lenses of theoptical imaging system illustrated in FIG. 5 .

FIG. 9 is a lens configuration diagram of an optical imaging systemaccording to a third example.

FIG. 10 is a set of graphs illustrating curves representing aberrationcharacteristics of the optical imaging system illustrated in FIG. 9 .

FIG. 11 is a table listing lens characteristics of the optical imagingsystem illustrated in FIG. 9 ; and

FIG. 12 is a table listing aspherical coefficients of lenses of theoptical imaging system illustrated in FIG. 9 .

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements, where applicable. The drawings maynot be to scale, and the relative size, proportions, and depiction ofelements in the drawings may be exaggerated for clarity, illustration,or convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure. The sequences of operations described herein are merelyexamples, and are not limited to those set forth herein, but may bechanged, as will be apparent after an understanding of the disclosure,with the exception of operations necessarily occurring in a certainorder. Also, descriptions of functions and constructions that are wellknown may be omitted for increased clarity and conciseness.

The features described herein may be embodied in different forms, andshould not be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided so thatthis disclosure will be thorough and complete, and will convey the fullscope of the disclosure to one of ordinary skill in the art.

Throughout the specification, it will be understood that when anelement, such as a layer, region or wafer (substrate), is referred to asbeing “on,” “connected to,” or “coupled to” another element, it can bedirectly “on,” “connected to,” or “coupled to” the other element, orother elements intervening therebetween may be present. In contrast,when an element is referred to as being “directly on,” “directlyconnected to,” or “directly coupled to” another element, there may be noelements or layers intervening therebetween. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various components, regions, or sections, these components,regions, or sections are not to be limited by these terms, unlessotherwise noted. Rather, these terms are only used to distinguish onecomponent, region, or section from another component, region, orsection. Thus, a first component, region, or section referred to inexamples described herein may also be referred to as a second component,region, or section without departing from the teachings of the examples.

The articles “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. The terms“comprises,” “includes,” and “has” specify the presence of statedfeatures, numbers, operations, members, elements, and/or combinationsthereof, but do not preclude the presence or addition of one or moreother features, numbers, operations, members, elements, and/orcombinations thereof.

Due to manufacturing techniques and/or tolerances, variations of theshapes shown in the drawings may occur. Thus, the examples describedherein are not limited to the specific shapes shown in the drawings, butinclude changes in shape that occur during manufacturing.

Subsequently, examples are described in further detail with reference tothe accompanying drawings. Examples provide an optical imaging systemallowing for device slimness, while implementing a relatively wide angleof view. Examples also provide an optical imaging system in which highresolution may be implemented while providing improved aberrationcorrection effects. In the lens configuration diagrams, the thickness,size, and shape of lenses as illustrated may be somewhat exaggerated forease of explanation, and shapes of spherical or aspherical surfacesillustrated in the lens configuration diagrams are only provided by wayof examples, and thus, are not limited thereto.

A first lens refers to a lens closest to an object, while a sixth lensrefers to a lens closest to an image sensor. In accordance withillustrative examples, the embodiments described of the optical imagingsystem include six lenses with a refractive power. However, the numberof lenses in the optical imaging system may vary in some embodiments,for example, between two to six lenses, while achieving one or moreresults and benefits described below. Also, although each lens isdescribed with a particular refractive power, a different refractivepower for at least one of the lenses may be used to achieve the intendedresult.

In the case of respective lenses, a first surface refers to a surface(or an object-side surface) closest to an object, and a second surfacerefers to a surface (or an image-side surface) closest to an imagingplane. In the present specification, all of radii of curvature,thicknesses of lenses, and the like are provided in millimeters (mm),and the unit of angle of view of an optical imaging system (FOV) isdegrees. A person skilled in the relevant art will appreciate that otherunits of measurement may be used. Further, in embodiments, all radii ofcurvature, thicknesses, OALs (optical axis distances from the firstsurface of the first lens to the image sensor), a distance on theoptical axis between the stop and the image sensor (SLs), image heights(IMGHs) (image heights), and back focus lengths (BFLs) of the lenses, anoverall focal length of an optical imaging system, and a focal length ofeach lens are indicated in millimeters (mm). Likewise, thicknesses oflenses, gaps between the lenses, OALs, TLs, SLs are distances measuredbased on an optical axis of the lenses.

In addition, in descriptions of shapes of respective lenses, the meaningthat one surface of a lens is convex is that a portion of a paraxialregion of the surface is convex, and the meaning that one surface of alens is concave is that a portion of a paraxial region of the surface isconcave. Thus, even in the case that it is described that one surface ofa lens is convex, an edge portion of the lens may be concave. Similarly,even in the case that it is described that one surface of a lens isconcave, an edge portion of the lens may be convex. The paraxial regionrefers to a relatively narrow region in the vicinity of an optical axis.In other words, a paraxial region of a lens may be convex, while theremaining portion of the lens outside the paraxial region is eitherconvex, concave, or flat. Further, a paraxial region of a lens may beconcave, while the remaining portion of the lens outside the paraxialregion is either convex, concave, or flat. In addition, in anembodiment, thicknesses and radii of curvatures of lenses are measuredin relation to optical axes of the corresponding lenses.

An optical imaging system according to an example includes a first lens,a second lens, a third lens, a fourth lens, a fifth lens, and a sixthlens sequentially arranged from an object side to an imaging plane.However, the optical imaging system according to examples is not limitedto only being configured of lenses, but may further include othercomponents as required. For example, the optical imaging system mayfurther include an image sensor converting an image of an incidentsubject into an electric signal.

In addition, the optical imaging system may further include an infraredfilter blocking infrared light. The infrared filter may be disposedbetween the sixth lens and the image sensor. The optical imaging systemmay further include a stop adjusting an amount of light. For example,the stop is disposed between the second lens and the third lens.

The first to sixth lenses configuring the optical imaging systemaccording to an example may be formed of a plastic material. At leastone lens of the first to sixth lenses has an aspherical surface. Inaddition, each of the first to sixth lenses may have at least oneaspherical surface. For example, at least one of first and secondsurfaces of each of the first to sixth lenses is an aspherical surface.In this case, the aspherical surfaces of the first to sixth lenses arerepresented by Equation 1 below.

$\begin{matrix}{Z = {\frac{{cY}^{2}}{1~\sqrt{1 - {\left( {1 + K} \right)c^{2}\mspace{14mu} Y^{2}}}} + {AY}^{4} + {BY}^{6} + {CY}^{8} + {DY}^{10} + {EY}^{12} + {FY}^{14} + \ldots}} & (1)\end{matrix}$

In Equation 1, c indicates curvature of a lens (an inverse number of aradius of curvature of a lens), K represents a conic constant, and Yindicates a distance from a certain point on an aspherical surface of alens to an optical axis. In addition, constants A to F refer toaspherical coefficients, and Z indicates a distance between a certainpoint on an aspherical surface of a lens to an apex of the asphericalsurface.

The optical imaging system including the first to sixth lenses may havenegative, positive, positive, negative, positive, negative refractivepowers sequentially from an object side to an imaging plane. The opticalimaging system according to an example satisfies Conditional Expressions1-8 below.0.5<f/f3<5.0   (Conditional Expression 1)20<v1−v6<60   (Conditional Expression 2)0<TTL/FOV<0.1   (Conditional Expression 3)1.60<n4<2.10   (Conditional Expression 4)3.0<TTL/f<4.0   (Conditional Expression 5)0.7<(R9−R10)/(R9+R10)<0.9   (Conditional Expression 6)0.5<|f/f1|<0.7   (Conditional Expression 7)0.2<|f1/f2|<0.4   (Conditional Expression 8)

In Conditional Expressions 1-8, f represents a total focal length of theoptical imaging system, f3 represents a focal length of the third lens,v1 represents an Abbe number of the first lens, v6 represents an Abbenumber of the sixth lens, TTL represents a distance from an object-sidesurface of the first lens to an imaging plane of an image sensor, FOVrepresents an angle of view of the optical imaging system, n4 representsa refractive index of the fourth lens, R9 represents a radius ofcurvature of an object-side surface of the fifth lens, R10 represents aradius of curvature of an image-side surface of the fifth lens, f1represents a focal length of the first lens, and f2 represents a focallength of the second lens.

In an example, when an upper limit of Conditional Expression 1 isexceeded, distortion aberration is increased. In the case of beingoutside of a lower limit of Conditional Expression 1, the refractivepower of the third lens may be decreased, causing the occurrence ofcurvature of an image surface thereof and thereby causing a decrease inresolution of an imaging plane peripheral portion of the image sensor.

In another example, when an upper limit of Conditional Expression 2 isexceeded, cost competitiveness of the fourth lens may be decreased. Inthe case of being outside of a lower limit of Conditional Expression 2,it may be difficult to correct chromatic aberrations and implement highresolving power.

As an example, when an upper limit of Conditional Expression 3 isexceeded, an overall length of an optical imaging system may beincreased and thus it may be difficult to implement miniaturization. Inthe case of being outside of a lower limit value of ConditionalExpression 3, an angle of view of the optical imaging system may besignificantly decreased.

For another example, when an upper limit of Conditional Expression 4 isexceeded, cost competitiveness of the fourth lens may be decreased. Inthe case of being outside of a lower limit of Conditional Expression 4,it may be difficult to correct chromatic aberrations and implement highresolving power.

Hereinafter, the first to sixth lenses constituting the optical imagingsystem according to an example will be described. The first lens has anegative refractive power. In addition, the first lens may have ameniscus shape convex toward an object. In an embodiment, a firstsurface of the first lens is convex in a paraxial region, and a secondsurface of the first lens is concave in the paraxial region. In adifferent embodiment, the first lens has a shape in which both surfacesare concave. For example, the first surface and the second surface ofthe first lens are concave in the paraxial region.

In the case of the first lens, at least one surface of the first surfaceand the second surface may be aspherical. In an embodiment, bothsurfaces of the first lens are aspherical.

The second lens has a positive refractive power. In addition, the secondlens may have a meniscus shape convex toward an object. In anembodiment, a first surface of the second lens is convex in a paraxialregion, and a second surface is concave in the paraxial region. In thecase of the second lens, at least one of the first surface and thesecond surface may be aspherical. For example, both surfaces of thesecond lens are aspherical.

The third lens has a positive refractive power. In addition, the thirdlens may have a shape in which both surfaces are convex. For example,the first surface and the second surface of the third lens are convex inthe paraxial region. In the case of the third lens, at least one of thefirst surface and the second surface may be aspherical. In anembodiment, both surfaces of the third lens are aspherical.

The fourth lens has a negative refractive power. In addition, the fourthlens may have a meniscus shape convex toward the object. For example, afirst surface of the fourth lens is convex in a paraxial region, and asecond surface is concave in the paraxial region. In the case of thefourth lens, at least one of the first surface and the second surfacemay be aspherical. In an embodiment, both surfaces of the fourth lensare aspherical.

The fifth lens has a positive refractive power. In addition, the fifthlens may have a meniscus shape convex toward an imaging plane. Forexample, a first surface of the fifth lens is concave in a paraxialregion, and a second surface is convex in the paraxial region. In thecase of the fifth lens, at least one of the first surface and the secondsurface may be aspherical. In an embodiment, both surfaces of the fifthlens are aspherical.

The sixth lens has a negative refractive power. In addition, the sixthlens may have a meniscus shape convex toward the object. For example, afirst surface of the sixth lens is convex in a paraxial region, and asecond surface is concave in the paraxial region. In the case of thesixth lens, at least one of the first surface and the second surface maybe aspherical. In an embodiment, both surfaces of the sixth lens areaspherical.

In addition, the sixth lens may have at least one inflection pointformed on at least one of first and second surfaces. For example, thefirst surface of the sixth lens has a convex shape in the paraxialregion, but concave shape toward an edge region. The second surface ofthe sixth lens may have a concave shape in the paraxial region, but aconvex shape toward an edge region.

In the optical imaging system configured as described above, aberrationcorrection performance may be improved because a plurality of lensesperforms an aberration correction function.

An optical imaging system according to a first example will be describedwith reference to FIGS. 1 to 4 . The optical imaging system according tothe first example includes a first lens 110, a second lens 120, a thirdlens 130, a fourth lens 140, a fifth lens 150, and a sixth lens 160. Theoptical imaging system according to the first example may furtherinclude a stop ST, an infrared light blocking filter 170, and an imagesensor 180.

Lens characteristics of respective lenses, such as radii of curvature oflenses, lens thicknesses, distances between lenses, refractive indexesand Abbe numbers, are provided as listed in the table of FIG. 3 . Atotal focal length f of the optical imaging system according to thefirst example is 1.6 mm, a focal length f1 of the first lens is −2.666mm, a focal length f2 of the second lens is 7.278 mm, a focal length f3of the third lens is 1.906 mm, a focal length f4 of the fourth lens is−3.807 mm, a focal length f5 of the fifth lens is 1.492 mm, and a focallength f6 of the sixth lens is −2.312 mm.

A constant F-number, indicating a brightness of the optical imagingsystem, is 2.4. A distance TTL from an object-side surface of the firstlens to an imaging plane of the image sensor is 4.999 mm and an angle ofview (FOV) of the optical imaging system is 115 degrees. A distance BFLfrom an image-side surface of the sixth lens to the imaging plane of theimage sensor is 1.132 mm.

In the first example, first lens 110 has a negative refractive power, afirst surface of first lens 110 is convex in a paraxial region, and asecond surface of first lens 110 is concave in the paraxial region. Thesecond lens 120 has a positive refractive power, a first surface ofsecond lens 120 is convex in a paraxial region, and a second surface ofsecond lens 120 is concave in the paraxial region. The third lens 130has a positive refractive power, and first and second surfaces of thirdlens 130 are convex in a paraxial region.

The fourth lens 140 has a negative refractive power, a first surface offourth lens 140 is convex in a paraxial region, and a second surface offourth lens 140 is concave in the paraxial region. The fifth lens 150has a positive refractive power, a first surface of fifth lens 150 isconcave in a paraxial region, and a second surface of fifth lens 150 isconvex in the paraxial region. The sixth lens 160 has a negativerefractive power, a first surface of sixth lens 160 is convex in aparaxial region, and a second surface of sixth lens 160 is concave inthe paraxial region. In addition, sixth lens 160 has at least oneinflection point on at least one of the first surface and the secondsurface.

Respective surfaces of first to sixth lenses 110 to 160 have anaspherical coefficient as illustrated in FIG. 4 . For example, all ofobject-side surfaces and image-side surfaces of first to sixth lenses110 to 160 may be aspherical surfaces. Optionally, a stop ST may bedisposed between second lens 120 and third lens 130. The optical imagingsystem configured as described above may have aberration characteristicsas illustrated by the graphs in FIG. 2 .

With reference to FIGS. 5 to 8 , an optical imaging system according toa second example will be described below. The optical imaging systemaccording to the second example includes a first lens 210, a second lens220, a third lens 230, a fourth lens 240, a fifth lens 250, and a sixthlens 260. The optical imaging system according to the second example mayfurther include a stop ST, an infrared light blocking filter 270, and animage sensor 280.

Lens characteristics of respective lenses, such as radii of curvature oflenses, lens thicknesses, distances between lenses, refractive indexesand Abbe numbers, are provided as listed in the table of FIG. 7 . Atotal focal length f of the optical imaging system according to thesecond example is 1.6 mm, a focal length f1 of the first lens is −2.667mm, a focal length f2 of the second lens is 9.265 mm, a focal length f3of the third lens is 1.896 mm, a focal length f4 of the fourth lens is−3.907 mm, a focal length f5 of the fifth lens is 1.48 mm, and a focallength f6 of the sixth lens is −2.276 mm.

A constant F-number, indicating a brightness of the optical imagingsystem, is 2.45. A distance TTL from an object-side surface of the firstlens to an imaging plane of the image sensor is 5.199 mm and an angle ofview (FOV) of the optical imaging system is 115 degrees. A distance BFLfrom an image-side surface of the sixth lens to the imaging plane of theimage sensor is 1.126 mm.

In the second example, the first lens 210 has a negative refractivepower, a first surface of first lens 210 is convex in a paraxial region,and a second surface of first lens 210 is concave in the paraxialregion. The second lens 220 has a positive refractive power, a firstsurface of second lens 220 is convex in a paraxial region, and a secondsurface of second lens 220 is concave in the paraxial region. The thirdlens 230 has a positive refractive power, and first and second surfacesof third lens 230 are convex in a paraxial region.

The fourth lens 240 has a negative refractive power, a first surface offourth lens 240 is convex in a paraxial region, and a second surface offourth lens 240 is concave in the paraxial region. The fifth lens 250has a positive refractive power, a first surface of fifth lens 250 isconcave in a paraxial region, and a second surface of fifth lens 250 isconvex in the paraxial region. The sixth lens 260 has a negativerefractive power, a first surface of sixth lens 260 is convex in aparaxial region, and a second surface of sixth lens 260 is concave inthe paraxial region. In addition, sixth lens 260 has at least oneinflection point on at least one of the first surface and the secondsurface.

Respective surfaces of first to sixth lenses 210 to 260 have anaspherical coefficient as listed in FIG. 8 . For example, all ofobject-side surfaces and image-side surfaces of first to sixth lenses210 to 260 are aspherical surfaces. Optionally, a stop ST may bedisposed between second lens 220 and third lens 230. The optical imagingsystem configured as described above may have aberration characteristicsas illustrated by the graphs in FIG. 6 .

With reference to FIGS. 9 to 12 , an optical imaging system according toa third example will be described below. The optical imaging systemaccording to the third example includes a first lens 310, a second lens320, a third lens 330, a fourth lens 340, a fifth lens 350, and a sixthlens 360. The optical imaging system according to the third example mayfurther include a stop ST, an infrared light blocking filter 370, and animage sensor 380.

Lens characteristics of respective lenses, such as radii of curvature oflenses, lens thicknesses, distances between lenses, refractive indexesand Abbe numbers, are provided as listed in the table of FIG. 11 . Atotal focal length f of the optical imaging system according to thethird example is 1.645 mm, a focal length f1 of the first lens is −2.105mm, a focal length f2 of the second lens is 4.381 mm, a focal length f3of the third lens is 1.418 mm, a focal length f4 of the fourth lens is−2.929 mm, a focal length f5 of the fifth lens is 2.004 mm, and a focallength f6 of the sixth lens is −2.843 mm.

A constant F-number, indicating a brightness of the optical imagingsystem, is 2.25. A distance TTL from an object-side surface of the firstlens to an imaging plane of the image sensor is 5.15 mm and an angle ofview (FOV) of the optical imaging system is 120 degrees. A distance BFLfrom an image-side surface of the sixth lens to the imaging plane of theimage sensor is 1.109 mm.

In the third example, the first lens 310 has a negative refractivepower, and first and second surfaces of first lens 310 are concave in aparaxial region. The second lens 320 has a positive refractive power, afirst surface of second lens 320 is convex in a paraxial region, and asecond surface of second lens 320 is concave in the paraxial region. Thethird lens 330 has a positive refractive power, and first and secondsurfaces of third lens 330 are convex in a paraxial region.

The fourth lens 340 has a negative refractive power, a first surface offourth lens 340 is convex in a paraxial region, and a second surface offourth lens 340 is concave in the paraxial region. The fifth lens 350has a positive refractive power, a first surface of fifth lens 350 isconcave in a paraxial region, and a second surface of fifth lens 350 isconvex in the paraxial region. The sixth lens 360 has a negativerefractive power, a first surface of sixth lens 360 is convex in aparaxial region, and a second surface of sixth lens 360 is concave inthe paraxial region. In addition, sixth lens 360 has at least oneinflection point on at least one of the first surface and the secondsurface thereof.

Respective surfaces of first to sixth lenses 310 to 360 have anaspherical coefficient as listed in FIG. 12 . For example, all ofobject-side surfaces and image-side surfaces of first to sixth lenses310 to 360 are aspherical surfaces. Optionally, a stop ST may bedisposed between second lens 320 and third lens 330. The optical imagingsystem configured as described above may have aberration characteristicsas illustrated by the graphs in FIG. 10 .

As set forth above, in the case of an optical imaging system accordingto an example, a slim optical imaging system may be implemented whilehaving a relatively wide angle of view. In addition, relatively highresolution may be implemented while providing improved aberrationcorrection effects.

While this disclosure includes specific examples, it will be apparentafter an understanding of the application that various changes in formand details may be made in these examples without departing from thespirit and scope of the claims and their equivalents. The examplesdescribed herein are to be considered in a descriptive sense only, andnot for purposes of limitation. Descriptions of features or aspects ineach example are to be considered as being applicable to similarfeatures or aspects in other examples.

Suitable results may be achieved if the described techniques areperformed in a different order, and/or if components in a describedsystem, architecture, device, or circuit are combined in a differentmanner, and/or replaced or supplemented by other components or theirequivalents. Therefore, the scope of the disclosure is defined not bythe detailed description, but by the claims and their equivalents, andall variations within the scope of the claims and their equivalents areto be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system comprising: a firstlens having a negative refractive power and a concave image-side surfacealong an optical axis; a second lens having a positive refractive powerand a concave image-side surface along the optical axis; a third lenshaving a refractive power and a convex object-side surface along theoptical axis; a fourth lens having refractive power and a convexobject-side surface along the optical axis; a fifth lens having positiverefractive power, a concave object-side surface along the optical axis,and a convex image-side surface along the optical axis; and a sixth lenshaving a negative refractive power, wherein the first to sixth lensesare sequentially arranged in ascending numerical order along an opticalaxis from an object side of the optical imaging system toward an imagingplane of the optical imaging system, and 0.2<|f1/f2|<0.4 is satisfied,where f1 is a focal length of the first lens and f2 is a focal length ofthe second lens.
 2. The optical imaging system of claim 1, wherein thefirst lens has a convex object-side surface along the optical axis. 3.The optical imaging system of claim 1, wherein the second lens has aconvex object-side surface along the optical axis.
 4. The opticalimaging system of claim 1, wherein the sixth lens has a convexobject-side surface along the optical axis and a concave image-sidesurface along the optical axis.
 5. The optical imaging system of claim1, wherein an angle of view of the optical imaging system is 100 degreesor more.
 6. The optical imaging system of claim 1, wherein 20<v1−v6<60is satisfied, where v1 is an Abbe number of the first lens and v6 is anAbbe number of the sixth lens.
 7. The optical imaging system of claim 1,wherein 0<TTL/FOV<0.1 is satisfied, where TTL is a distance along theoptical axis from an object-side surface of the first lens to theimaging plane and FOV is an angle of view of the optical imaging system.8. An optical imaging system comprising: a first lens having a negativerefractive power; a second lens having a meniscus shape and a refractivepower; a third lens having a positive refractive power; a fourth lenshaving a refractive power; a fifth lens having a refractive power; and asixth lens having a refractive power, wherein the first to sixth lensesare sequentially arranged in ascending numerical order along an opticalaxis from an object side of the optical imaging system toward an imagingplane of the optical imaging system, wherein 0<TTL/FOV<0.1, where TTL isa distance along the optical axis from an object-side surface of thefirst lens to the imaging plane and FOV is an angle of view of theoptical imaging system, wherein 0.7<(R9−R10)/(R9+R10)<0.9, where R9 is aradius of curvature of an object-side surface of the fifth lens and R10is a radius of curvature of an image-side surface of the fifth lens,wherein 3.0<TTL/f<4.0, where f is a total focal length of the opticalimaging system, and wherein 20<v1−v6<60, where v1 is an Abbe number ofthe first lens and v6 is an Abbe number of the sixth lens.
 9. Theoptical imaging system of claim 8, wherein 0.2<|f1/f2|<0.4, where f1 isa focal length of the first lens and f2 is a focal length of the secondlens.
 10. The optical imaging system of claim 8, wherein 0.5<|f/f1|<0.7,where f1 is a focal length of the first lens.
 11. An optical imagingsystem comprising: a first lens having a negative refractive power; asecond lens having a meniscus shape and a refractive power; a third lenshaving a positive refractive power; a fourth lens having a refractivepower; a fifth lens having a refractive power; and a sixth lens having arefractive power, wherein the first to sixth lenses are sequentiallyarranged in ascending numerical order along an optical axis from anobject side of the optical imaging system toward an imaging plane of theoptical imaging system, wherein 0<TTL/FOV<0.1, where TTL is a distancealong the optical axis from an object-side surface of the first lens tothe imaging plane and FOV is an angle of view of the optical imagingsystem, wherein 0.7<(R9−R10)/(R9+R10)<0.9, where R9 is a radius ofcurvature of an object-side surface of the fifth lens and R10 is aradius of curvature of an image-side surface of the fifth lens, wherein3.0<TTL/f<4.0, where f is a total focal length of the optical imagingsystem, and 0.2<|f1/f2|<0.4, where f1 is a focal length of the firstlens and f2 is a focal length of the second lens.
 12. The opticalimaging system of claim 11, wherein 20<v1−v6<60, where v1 is an Abbenumber of the first lens and v6 is an Abbe number of the sixth lens.